dswap.c

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/* DSWAP.F -- translated by f2c (version 19941215).
   You must link the resulting object file with the libraries:
        -lf2c -lm   (in that order)
*/

#include "f2c.h"
#include "cblasimpexp.h"

/* Subroutine */ int __IMPEXP__ dswap_(n, dx, incx, dy, incy)
integer *n;
doublereal *dx;
integer *incx;
doublereal *dy;
integer *incy;
{
    /* System generated locals */
    integer i__1;

    /* Local variables */
    static integer i, m;
    static doublereal dtemp;
    static integer ix, iy, mp1;


/*     interchanges two vectors. */
/*     uses unrolled loops for increments equal one. */
/*     jack dongarra, linpack, 3/11/78. */


    /* Parameter adjustments */
    --dy;
    --dx;

    /* Function Body */
    if (*n <= 0) {
        return 0;
    }
    if (*incx == 1 && *incy == 1) {
        goto L20;
    }

/*       code for unequal increments or equal increments not equal */
/*         to 1 */

    ix = 1;
    iy = 1;
    if (*incx < 0) {
        ix = (-(*n) + 1) * *incx + 1;
    }
    if (*incy < 0) {
        iy = (-(*n) + 1) * *incy + 1;
    }
    i__1 = *n;
    for (i = 1; i <= i__1; ++i) {
        dtemp = dx[ix];
        dx[ix] = dy[iy];
        dy[iy] = dtemp;
        ix += *incx;
        iy += *incy;
/* L10: */
    }
    return 0;

/*       code for both increments equal to 1 */


/*       clean-up loop */

L20:
    m = *n % 3;
    if (m == 0) {
        goto L40;
    }
    i__1 = m;
    for (i = 1; i <= i__1; ++i) {
        dtemp = dx[i];
        dx[i] = dy[i];
        dy[i] = dtemp;
/* L30: */
    }
    if (*n < 3) {
        return 0;
    }
L40:
    mp1 = m + 1;
    i__1 = *n;
    for (i = mp1; i <= i__1; i += 3) {
        dtemp = dx[i];
        dx[i] = dy[i];
        dy[i] = dtemp;
        dtemp = dx[i + 1];
        dx[i + 1] = dy[i + 1];
        dy[i + 1] = dtemp;
        dtemp = dx[i + 2];
        dx[i + 2] = dy[i + 2];
        dy[i + 2] = dtemp;
/* L50: */
    }
    return 0;
} /* dswap_ */

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